1. Field of the Invention
The present invention relates generally to a communication protocol structure, a data transmission/reception method, and a handover method of a Mobile Subscriber Station (MSS) in a wireless communication system, and more particularly to a divided Media Access Control (MAC) protocol structure, and a data transmission and reception method, and a handover method and system using the structure in a wireless communication system, which reduces the load of the wireless communication system using session information and improves communication quality.
2. Description of the Related Art
Currently, with the development of the mobile communication industry and the increased demand for an Internet service, the need for a mobile communication system capable of efficiently providing a wireless Internet service is increasing more and more. Because an existing mobile communication network has been developed to provide a voice-centered service, it has disadvantages in that a data transmission bandwidth is relatively narrow and service charge is expensive.
An Institute of Electrical and Electronics Engineers (IEEE) 802.16e standardization group of the IEEE, which is one of an international standardization organization, is pushing establishment of an IEEE 802.16d standard, which is to be used as the standard for providing a wireless broadband Internet service to a fixed subscriber station. Simultaneously, the IEEE 802.16e standardization group is pushing the establishment of the IEEE 802.16e standard by improving the IEEE 802.16d standard in order to provide the wireless broadband Internet service to an MSS.
Compared with a conventional wireless technology for a voice service, the IEEE 802.16d standard and the IEEE 802.16e standard enable mass storage data to be transmitted within a short time due to a wide bandwidth of data and enable channels to be efficiently used due to the sharing of the channels by all users. However, the IEEE 802.16d standard does not reflect an MSS because it considers only a fixed subscriber station. Further, because the IEEE 802.16e standard, which is being developed for providing a wireless Internet service to an MSS by improving the IEEE 802.16d standard, has also been developed on the basis of the IEEE 802.16d standard, the IEEE 802.16e standard does not sufficiently have the functions required for providing the service to the MSS. A representative service function for the MSS may include a handover function, a paging function, a power consumption saving function, etc. From among these functions, the handover function is an essential function in providing the service to the MSS.
The handover function changes an Access Point (AP) providing a communication service to the MSS due to the movement of the MSS. Accordingly, in order to continuously provide the communication service to the MSS, it is essential to retain session information between the MSS and the AP performing the handover. The session information includes a transmission state of data, functions and characteristics of the MSS, functions and characteristics of the AP, authentication information for the MSS, etc., which are required for communication between the MSS and the AP.
FIG. 1 is a diagram illustrating a conventional handover process of an MSS in a broadband wireless communication system. Referring to FIG. 1, an MSS 10 is connected to an Access Point (AP) 20a or 20b through a wireless network. The APs 20a and 20b are connected to a router 30 through a wire network 1, such that the MSS 10 and the APs 20a and 20b transmit/receive packet data to/from an external Internet Protocol (IP) network such as an Internet. Further, session information between the MSS 10 and the APs 20a and 20b is stored in both the MSS 10 and the APs 20a and 20b. Accordingly, the MSS 10 and the APs 20a and 20b continuously manage the same session information.
However, when the MSS 10 moves from a currently connected Serving AP (S-AP) 20a and is handed over to a newly connected Target AP (T-AP) 20b, the MSS 10 may continuously manage the already stored session information regardless of the handover. However, because the T-AP 20b does not know the session information managed by the S-AP 20a, it is difficult to manage the same session information.
Accordingly, the handover process of the MSS 10 requires transfer of the session information between the S-AP 20a and the T-AP 20b and the establishment of new session information between the MSS 10 and the T-AP 20b. However, when a large quantity of session information must be transferred to the T-AP 20b in the handover, it takes more time to transfer the session information and establish the new session information. In addition, the MSS 10 does not receive a service from the S-AP 20a and the T-AP 20b during the transfer of the session information and the establishment of new session information.